1. Field of the Invention
The present invention relates to an automobile seat slide unit for use in adjusting the position of a seat in a direction longitudinally of a vehicle body.
2. Description of Related Art
FIG. 1 depicts a conventional automobile slide rail assembly as disclosed in Japanese Laid-Open Utility Model Application (unexamined) No. 448034, which includes a lower rail 1 secured to a vehicle floor and an upper rail 2 secured to a seat and slidably mounted on the lower rail 1.
The lower rail 1 includes a lock plate 4 secured thereto and having a plurality of lock grooves 4a defined therein at regular intervals in a direction longitudinally thereof, while the upper rail 2 includes a lock lever 3 pivotally mounted thereon and having a lock finger 3a that is engageable with one of the lock grooves 4a of the lock plate 4 to lock the seat.
In the above-described conventional slide rail assembly, however, because the lock lever 3, the lock plate 4 and the like are disposed outside the two rails 1, 2, not only the space in which legs of a rear seat occupant are placed is limited, but also the freedom of the layout or arrangement of the seat or other units adjacent thereto such as, for example, a tilt unit, a seat lift unit and the like, are limited. In addition, the seat slide unit of FIG. 1 has many component parts and is hence costly and heavy.
To overcome such problems, there has been proposed another slide rail assembly as shown in FIG. 2, which includes a lower rail 1 and an upper rail 2 slidably mounted on the lower rail 1. The lower rail 1 has a bottom wall 1a, two inner side walls 1b extending upwardly from respective side edges of the bottom wall 1a, and two outer side walls 1c extending laterally outwardly and downwardly from respective upper edges of the inner side walls 1b to present a shape generally similar to the inverted shape of a figure "U". The upper rail 2 has an upper wall 2a, two outer side walls 2b extending downwardly from respective side edges of the upper wall 2a, and two inner side walls 2c extending laterally inwardly and upwardly from respective lower edges of the outer side walls 2b to represent a shape generally similar to the shape of a figure "U". In this construction, the outer side walls 2b of the upper rail 2 are located outside the associated outer side walls 1c of the lower rail 1, while the inner side walls 2c of the upper rail 2 are received within respective guide clearances each defined between the inner and outer side walls 1b, 1c of the lower rail 1 in a generally handshake fashion.
The slide rail assembly of FIG. 2 also includes a plurality of spherical members 3 interposed between an internal surface of the upper rail 2 and an external surface of the lower rail 1 at upper corners thereof, and two generally U-shaped resinous retainers 4 interposed between lower ends of the outer side walls 1c of the lower rail 1 and the associated laterally inwardly extending portions of the upper rail 2.
In this slide rail assembly, however, because the resinous retainers 4 are held in sliding contact with the upper and lower rails 2, 1, reducing looseness between the former and the latter results in an increase in the required operating force, while reducing the operating force results in increased in looseness.